This PR was discussed at length at the latest dev meeting, and @wtbarnes needs to write his thoughts here

As mentioned above, there was some discussion of this PR at the community call approximately two weeks ago. I'll try my best to summarize here:

• Models of the stratified solar atmosphere, particularly in the chromosphere are widely used throughout the community, both in data analysis and modeling (e.g. as an initial condition for hydrodynamic models). There is no easy, standard way to access these models and as such this functionality is needed.
• I expressed reservations about these living in the core package (sunpy) as well as the Project taking ownership of these models. Are we sure we want to be the caretakers of these models until the end of time? Are these canonical enough to live in core or would they be better suited in an existing or new affiliated package?
• Given that the data from these papers is not licensed, there is a question of whether we are even allowed to distribute these data. @nabobalis (I think?) was going to contact ApJ to ask about this. We should also consider contacting the authors.
• We should expose multiple atmospheric models, not just this one (though I believe it is considered the most up to date). Other models to consider:
  • https://ui.adsabs.harvard.edu/abs/1973ApJ...184..605V/abstract
  • https://ui.adsabs.harvard.edu/abs/1976ApJS...30....1V/abstract
  • https://ui.adsabs.harvard.edu/abs/1981ApJS...45..635V/abstract (models A-F)
  • https://ui.adsabs.harvard.edu/abs/1990ApJ...355..700F/abstract
  • https://ui.adsabs.harvard.edu/abs/1991ApJ...377..712F/abstract
  • https://ui.adsabs.harvard.edu/abs/1993ApJ...406..319F/abstract
  • https://ui.adsabs.harvard.edu/abs/2002ApJ...572..636F/abstract
  • https://ui.adsabs.harvard.edu/abs/2006ApJ...639..441F/abstract
• Any implementation should be able to easily accommodate the addition of new models

Thank you again for this PR @parharti and I apologize that this PR has gone so long without a follow-up review.

We had some discussion today at the community meeting about this and we decided that we would like this to go into the core package, but that it probably makes sense to store these files elsewhere, most likely Zenodo, and then manage them using the remote data manager: https://docs.sunpy.org/en/stable/how_to/remote_data_manager.html#use-the-remote-data-manager. The idea would be to upload the latest table initially (probably the 2008 paper shown here as I believe it is the most recent and up to date model) and then upload later ones as needed. The hashes and URLs would be tracked here and downloaded as needed by the data manager.

This would alleviated the need to keep these files in the repository. Furthermore, if we feel that the number of models, either these atmospheres or some other atmospheric profile, is continually growing, these could be spun out into their own package.

@parharti As it has been a while, if you'd like, I could take over this PR and finish it up.

I'm going to mark this as draft until someone picks it up.

Hello 👋, Thanks for your contribution to sunpy!
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